Striascopic imaging of reflecting profiles with laser light and the interfacial tension of fluid interfaces

Publisher Website
Google Scholar
Abstract
Optical setting on the profiles of reflecting objects, solids or fluids, by striascopic imaging with parallel laser light can be accurate to better than +or-1 mu m, if the optical system is calibrated with spherical and cylindrical gauges of 1-5 mm radius. Upon tenfold magnification the symmetrical central black fringe on the photographic image is at least 70 mu m wide. Parallel laser light is very convenient in aligning all optical elements and renders the object focusing non-critical to +or-1.4 mm. The gauge data show that the striascopic image is not formed by reflective interference alone but also by diffraction. The smaller the aperture of the three-dimensional optical filter, the more diffraction will participate and the more closely the centre of the central black fringe must approach the geometrical image position. The method is applied to profile measurements of mercury drops in aqueous solution and to nitrogen bubbles in water, with diameters of 5-9 mm.

This publication has 13 references indexed in Scilit: